The management of ductal carcinoma in situ (DCIS) is a controversial topic among breast cancer specialists. Whether resection of these preinvasive lesions is always necessary remains under debate. But an ongoing multi-institutional clinical trial may help answer this question and perhaps change the treatment guidelines for patients with DCIS.

“This trial addresses the question of whether there is a group of women who have DCIS but have a very low risk of developing invading or spreading cancer—a group of women in whom we could use active surveillance and avoid unnecessary surgery,” said Alastair Thompson, M.D., a professor in the Department of Breast Surgical Oncology at The University of Texas MD Anderson Cancer Center and the national co-chair of the Comparison of Operative to Monitoring and Endocrine Therapy (COMET) trial for low-risk DCIS.

Dr. Thompson noted that while similar trials are under way in the United Kingdom, Europe, and Japan, “This is the first trial in the United States to compare guideline-concordant care with active surveillance in the setting of DCIS.”

Trial design

The COMET trial (No. ALLIANCEAFT-25) is now enrolling women 40–99 years old with newly diagnosed low-risk (i.e., grade I or II) DCIS. The patients are randomly assigned to receive guideline-concordant care, which consists of surgery with or without radiation and/or endocrine therapy (the treatment recommended by the National Comprehensive Cancer Network guidelines); or active surveillance, which consists of frequent diagnostic mammography plus endocrine therapy if such therapy is recommended by the physician and desired by the patient. Patients who are randomly assigned to either of these treatment arms but decline the assigned treatment are assigned to a third arm. Those patients receive the treatment of their choice but are excluded from the trial’s main analysis. Dr. Thompson and his colleagues plan to include 900 patients in their analysis.

Patients in the guideline-concordant care arm undergo diagnostic mammography every 12 months, and those in the active-surveillance arm undergo diagnostic mammography every 6 months. Patients in either arm who develop invasive cancer will be treated with the standard of care.

Outcome measures

The trial’s primary outcome measure is the proportion of patients who develop invasive cancer in the ipsilateral breast within 2 years. The 5-year rates of ipsilateral invasive cancer diagnosis will also be examined. Dr. Thompson and his colleagues hypothesize that the rates will be similar between the guideline-concordant care and active-surveillance groups.

The researchers will also compare the characteristics of patients who develop ipsilateral invasive cancer to those of patients who do not. Ultimately, the researchers hope to develop criteria to determine which patients are likely to benefit from surgery and which can safely receive active surveillance.

Dr. Thompson said, “Through this trial, we’re trying to change the way we do things for some of the more than 60,000 women who are diagnosed with DCIS each year.”